3-Phase Panel Used as Single-Phase

[BMacky]

A few issues here: I was asked to look over some inspection hits on a 3-phase, 208Y/120V sub-panel that an inspector had instructed should have feeders phase-taped black, orange (high-leg) and blue. My guess is he had the deadfront removed and saw that it was a 3-phase panel, and noticing phase B had no single pole breakers installed assumed it was the high leg. He also noted it was a delta configuration, but I could not ascertain where he came up with that information.

I reviewed the taping instructions he laid out and after opening the panel and testing it with my voltmeter found it was a 3-phase panel, but the phase B feeder was dead, not connected at the main. The installing electrician wired it for single phase and figured he could "waste" the positions where the feeder was not live. That or use up a spare panel?

Question: Is it OK to utilize a 3-phase panel as a single-phase panel?

My customer would love for me to phase tape the b-phase orange to satisfy the inspector, but ethically I don't feel right doing this. I'd rather know the answer to the initial question and do this right from the get-go. IF it is an improper install, I'd swap out the panel. If not, I'd simply bring it to the inspectors attention and explain the difference.

Any advice is appreciated. Thanks!

Bob

 

[brother]

Question: Is it OK to utilize a 3-phase panel as a single-phase panel?

Bob

there is nothing in the code that says you cannot use a 3 phase panel for a single phase.

Its OK to use a 3 phase as a single phase.

 

[BMacky]

there is nothing in the code that says you cannot use a 3 phase panel for a single phase.

Its OK to use a 3 phase as a single phase.

Thanks! :smile:

 

[russ]

The question I have is, if it's listed as three phase equipment, can it be used as single phase?
My first impression is to say no. I,d have to read the listing to see if it is defined.

 

[russ]

The center phase, if wire can not be marked orange because it,s not a high leg.
If the center phase were wire with one of the other phases how would you balance the load, with 2/3s of the breakers on one phase?

 

[jrannis]

A few issues here: I was asked to look over some inspection hits on a 3-phase, 208Y/120V sub-panel that an inspector had instructed should have feeders phase-taped black, orange (high-leg) and blue. My guess is he had the deadfront removed and saw that it was a 3-phase panel, and noticing phase B had no single pole breakers installed assumed it was the high leg. He also noted it was a delta configuration, but I could not ascertain where he came up with that information.

I reviewed the taping instructions he laid out and after opening the panel and testing it with my voltmeter found it was a 3-phase panel, but the phase B feeder was dead, not connected at the main. The installing electrician wired it for single phase and figured he could "waste" the positions where the feeder was not live. That or use up a spare panel?

Question: Is it OK to utilize a 3-phase panel as a single-phase panel?


My customer would love for me to phase tape the b-phase orange to satisfy the inspector, but ethically I don't feel right doing this. I'd rather know the answer to the initial question and do this right from the get-go. IF it is an improper install, I'd swap out the panel. If not, I'd simply bring it to the inspectors attention and explain the difference.

Any advice is appreciated. Thanks!

Bob

When you say "not connected at the main" do you mean it was not terminated on the OCP or is there anything to connect to ?
Could it be connected in the future?

I would tape it orange and install a sign on the panel cover that says "CAUTION HI LEG ABSENT" :grin:

 

[BMacky]

When you say "not connected at the main" do you mean it was not terminated on the OCP or is there anything to connect to ?
Could it be connected in the future?

I would tape it orange and install a sign on the panel cover that says "CAUTION HI LEG ABSENT" :grin:

Good call. I thought about someone later opening the main and thinking there was a loose connection or something, and possibly connecting it. Nothing is labeled other than the panel ID "Panel-C" which doesn't give anything away. I need to take a look and see what's happening at the main.

Thanks for the tip!


Bob

 

[dbuckley]

I would caution that when misusing a three phase panel on single phase that the maximum load of the panel is determined by the neutral bar; a 100A three phase panel cannot be used as a 300A single phase panel, the maximum current carrying capacity remains at 100A.

 

[Chris6245]

Not sure if it's NEC or a local thing but here we have to label the panel in a "perminant" fashon as to the voltage, phase colors and neutral color like;

120/208 3 phase
black, red, blue
Neutral-White
Fed from ****

Also have to post Arc Flash warning.

So in this case I would lable as;

120/240 1 phase ("B" phase dead)
Black, Red
Neutral-White

Should clear up anything in future work and if the B phase was ever energised then the label should be changed. But I see nothing wrong with using a panel below it's listing. Don't know how many 3 pole fused and non fused disconnects I've seen with only 1 or 2 legs being used.

 

[jerm]

Blue? What code section did he cite that said the third leg should be Blue? There's no requirement for Blue in the NEC. If the leg is high (and it can't be if it isn't connected) then mark it orange, but you can tape the other two purple and pink if you want to.

EDIT: Chris- What's the exact text of your Arc Flash warning? ("Warning: Arc Flash Possible" ??)

 

[Chris6245]

EDIT: Chris- What's the exact text of your Arc Flash warning? ("Warning: Arc Flash Possible" ??)

Pretty much...Although I have been known to add an "h" to (Arch) just to see if the inspector can speel...hehe oops that would be spell